Coastal engineering introduction

Coastal Engineering
Introduction
Engineering Applications
by Msc. Jorge C. Palma
2013-04-15

PART ONE. INTRODUCTION TO COASTAL PROCESSES
 1 Overview
 1.1 Some Terminology of the Coasts
 1.2 Examples of Coastal Engineering Projects

PART ONE. INTRODUCTION TO COASTAL PROCESSES. Typical
zones.

Examples of coastal engineering projects. Cuba. Western
Coasts

PART ONE. INTRODUCTION TO COASTAL PROCESSES. Beach
Nourishment. Planform and profile dynamic.

Examples of coastal engineering projects Varadero Beach
Nourishment. 5,0 million M3

Effects of groins interacting with longshore sediment
transport
Shore side Sea side

Maria La Gorda Beach & Groins. Forgetting big frame!

Maria La Gorda Beach & Groins. Forgetting big frame, but
lucky end!

lucky end!
Groins

lucky end!
Emerged terraces

lucky end!
Equilibrated beach profiles

lucky end!
Rocks on surface, yet beach profile is equilibrated

Cuba. Cristino Naranjo Breakwater. Tetrapods 25-ton
weight

Cuba. Cay Coco Roadway. 27 km with 15 bridges.

Cuba. Cay Coco Roadway. Bascule Bridge.

Camposoto Beach Study. Cadiz, Spain.

Camposoto Beach Study. Cadiz, Spain.
Cadiz Port
Ebb, Flood
currents
Ebb, Flood
currents
Estuaries

Sweden. Varholmen. Lile Varholmen Pier Enlargement

Sweden. Lile Varholmen Pier Enlargement

Denmark. Arkens Museum Channel

Coastal Engineering. Arken Channel Project

PART ONE. INTRODUCTION TO COASTAL PROCESSES. Sediment
Characteristics
 2 Sediment Characteristics
 2.1 Sand Composition
 2.2 Grain Sizes
 2.3 Shape
 2.4 Porosity
 2.5 Fall Velocity

Characteristics
 2. Sediment Characteristics
 2.1 Sand Composition (70 % from granitic mountains and quartz, 20 %
feldespar, there are from calcium carbonates precipitated and from
abrasion of coral reefs).
 2.2 Grain Sizes. Representative normal diameter is D50, for bimodal
samples: Mean diameter=(D84+D50+D16)/3
 2.3 Fall Velocity. According to Stockes law is:
where
ρs, sand density
ρ, sea water density
g, gravity
d, sand diameter
µ, dynamic viscosity for salt water (aprox. 1/1000 N s/m2), but depends on water temperature.

Characteristics. Scale of Sediment Size Classification.

 3 Long-Term Processes
 3.1 Relative Sea Level Change. For 2100 estimated between 0,5 and 1,0
m. higher due to earth warming process and climate changes

PART ONE. INTRODUCTION TO COASTAL PROCESSES. Goteborg
sea water levels
 HHW 170 +11, 69
MHW 100 +10, 99
LHW 52 +10, 51
MW 0 +9, 99
HLW -40 +9, 59
MLW -62 +9, 37
LLW -112 +8, 87
The average values refer to the year 2012. Uplift Coefficient 0, 16 cm / year
The design level for structures near the sea in Gothenburg specified in
comprehensive plan and is set at +12.5 which includes 1 m sea-level rise
as a result of a warmer climate.

PART ONE. INTRODUCTION TO COASTAL
PROCESSES. Coastal Protection Policies

 3 Long-Term Processes
 3.2 Equilibrium Beach Proﬁle
The concept of an equilibrium proﬁle, - is the average beach response to the
natural forcing- makes it possible to determine several beach responses to
changes in forcing.
The equilibrium profile depends on sediment size, wave height and
period, and water level.

PART TWO. HYDRODYNAMICS OF THE COASTAL ZONE
Profile erosion due to storm tides and waves

PART ONE. INTRODUCTION TO COASTAL PROCESSES.
Equilibrium profile response to sea level rise: Bruun’s rule.
Equilibrium profile response to sea level rise:
Bruun’s rule.
a. Volume of sand generated by horizontal
retreat R of equilibrium profile over vertical
distance (h∗ + B);
(b) volume of sand required to maintain an
equilibrium profile of active width W∗ owing to a
rise S in mean water level;
(c) landward (R) and upward (S) components of
profile translation to achieve equilibrium relative to
increased sea level.

PART TWO. HYDRODYNAMICS OF THE COASTAL ZONE
 4 Tides and Storm Surges
 4.1 Astronomical Tides (sea level variations by gravitational influence of
moon, ranging from cm. till several meters depending on location)
 4.2 Storm Surges (wind velocities from scale 1: pressure<980 mbar, 96-
110 mph, surge 5 ft, moderate damage till scale 5: pressure <920 winds
>155 mph surge >18 ft damage Catastrophic)

PART TWO. HYDRODYNAMICS OF THE COASTAL ZONE. Water
waves and wave induced Hydrodynamics. Linear Theory.
 5 Waves and Wave-Induced Hydrodynamics
 5.1 Water Wave Mechanics
 5.2 Cross-Shore and Longshore Currents
 η (x,t) = (H/2)cos(kx-σt) k=2π/L and σ=2π/T

PART TWO. HYDRODYNAMICS OF THE COASTAL ZONE. Water
waves and wave induced Hydrodynamics. Boussinesq Theory. Shallows waters
 Boundary conditions: Variable depth, propagation in x direction, depth
averaged velocity and free surface elevation.

PART TWO. HYDRODYNAMICS OF THE COASTAL ZONE.
Wave refraction, difraction, and reflection.
 Wave refraction is produced due to interaction of sea bottom in shallow waters with waves and
when bathimetry is parallel to the shore the Snell optical law can be applied with waves changing
direction to shallower waters.
 Wave difraction happens around the border of obstacles.
 Wave reflexion occurs in front of vertical walls producing stationary effects.
 Wave breaking happens in shallow waters when the heigh of wave is about 0,78 water depth.

Wave refraction, difraction, and reflection. Cuba. Bridges difraction.

Cross shore and longshore currents. Schematic of vertically descending eddies with arrows showing
the direction of breaker travel
 .
The energy radiation by obliquely incident waves and breaking produce
additional longshore currents.
Reflection of waves energy against shore produce crosshore currents

PART THREE. COASTAL RESPONSE
 6 Field Measurement Techniques and Analysis
 6.1 Beach Proﬁle Measurements
 6.2 Historical Shoreline Change. Planforms Charts
 6.3 Sediment transport rates

 8 Sediment Transport
 8.1 Incipient Sand Motion and Depth of Closure
 8.2 Longshore Sediment Transport
Forces on a sand particle in an inclined bed. Point A denotes the point of contact between two
particles. Cd and CL are drag and lift coefficient depending on Reynolds number R.
After moment balance:
Ʈc/( ρ s − ρ )gd= f (Re), Ʈc indicates critical bed
shear stress for Incipient motion for a uniform depth,
the left-hand side of Eq. is known as the critical
Shields parameter, denoted as Ψ c , which is used as
an indicator of incipient motion

PART THREE. COASTAL RESPONSE. Sediment transport
 Shields curve for the initiation of motion for steady ﬂow (Raudkivi 1967)

PART THREE. COASTAL RESPONSE. Sediment transport. Closure
depth.
Hallermeir Formula for closure depth:
The variables are here functions of time measured in years, H(t) e is the
significant wave height that is exceeded during only 12 h in the time t, and
T (t) e is the associated period.
Longshore sediment transport:
 Bedload transport, which is either in sheet flow or rolled along the bottom
 Suspended load, which is carried up within the fluid column and moved by currents
 Swash load, which is moved on the beach face by the swash.
For littoral transport:

 9 Modeling of Beaches and Shorelines
 9.1 Physical Modeling of Coastal Processes (wave basins and wave tanks)
 9.2 Analytical Modeling (analytical equations with exact solutions for
abstract models of problems, one, two or tridimensional equations)
 9.3 Numerical Modeling (One, two or tridimensional equations using
computing techniques and processing capacities, calibrated with labs
measurements and real data under specific boundary conditions. Some use
Boussinesq equation). Represent Short-term & Long-term coastal evolution
 How is the randomness of the wave ﬁeld to be included?
 Should one representative wave train or a stochastic approach with different wave scenarios be used and the
results ensemble averaged?
 How are the storms to be included, particularly because they play such a major role in the beach proﬁle?
 How are the tides to be included?

 9.1 Physical Modeling of Coastal Processes (wave basins and wave tanks)

 9.1 Physical Modeling of Coastal Processes (wave basins and wave tanks.
Breakwater modeling)

PART THREE. COASTAL RESPONSE. Modular diagram for generic
tridimensional coastal model

PART FOUR. SHORELINE MODIFICATION AND ANALYSIS
 10 Beach Fill and Soft Engineering Structures
 10.1 Beach Nourishment (Beach Fill)
 10.2 Submerged Berms (modifying the waves evolution)
 11 Hard Engineering Structures
 11.1 Perched Beach
 11.2 Groins
 11.3 Offshore Breakwaters
 11.4 Revetments
 11.5 Seawalls

 10.1 Beach Nourishment (Beach Fill)

 10.1 Beach Nourishment (Beach Fill, ”Rainbow method)

 Beach Fill. Qualitative illustration of three components of shoreline recession following a
beach nourishment project shown for two background erosion rates and initial nourished width of
75 m.

 14 Shoreline Management
 14.1 Options and Factors
 14.2 The Role of Setbacks and Construction Standards (frozen
construction shorelines spaces areas up to 500 m.)
 14.3 Protective Value of a Wide Beach

Adaptation of flood protection.

 1. Climate Change will have direct and indirect effects on Coastal Areas
 - water levels will increase
 - wave heights may increase in some areas
 - wave directions will change
 - frequency and intensity of storms will increase at least in some areas,
which might also cause more intensive wave conditions
 This will result in:
 2. Higher loads on the coast and on coastal structures
 - retreat of the coast
 - changed long-shore sediment transport

 3. without adaptation
 - increase in probability of failure
 - increase of flooded area
 - increase of water level in flooded area
 - higher risks in coastal areas
 4. with adaptation
 - higher costs for coastal protection

Swedish approach on sustainable use of coastal zones.

Varholmen. Existing Pier and Berthing Dolphins

Varholmen. Pier Enlargement Project

Varholmen. Pier Enlargement Project. Varholmen waves
hindcasting SMHI

Varholmen. Pier Enlargement Project. Varholmen
Bathimetry

Channel Typical Section A-A and slopes. Concept Solution
+ 1,65 m. surface level
28 m.
15,5 m. 3,15 m.2,5 m. 6,85 m.
Existing soil
Crushed rocks and
gravels
+ 0,35 m. water level
Concrete slabs
and blocks
Centerline
- 1,90 m. channel bottom

Channel Typical Section B-B and sheet pile walls. Concept
Solution
10,0 m.
Existing soil
+ 0,35 m. water level
- 1,90 m. channel bottom
- 9,30 m. sheet pile foot
Existing soil
- 9,30 m. sheet pile foot
sheet pile walls

Coastal Engineering. Arken Channel Project. Budget.

Coastal Engineering Design data
 Maritime boundaries
 Coastal topography and bathymetry
 Geology and soil parameters
 Existing coastal defences and maritimes structures
 Erosion trends. Land cover changes (50 years). Aerial photography,
satellites and surveys.
 Winds
 Waves regimes
 Currents
 Water sea level rise (long term, global changes)
 River and coastal sediment transport
 Areas of high ecological values and protection structures
 Coastal Management planning

General methods and toolkits in Coastal Engineering
 Databases
 Surveys and local campaings
 Numerical models
 Physical models
 Engineering references and projects
 Regional guidelines and coastal management policies

Approach to Coastal Engineering Problems
 Information review and analysis. Review of existing BBDDs, studies, projects and related technical information
 Problem definition of client and stakeholders needs, goals and guidelines
 Definitions of spacial/time scales and evaluation of main natural and human actions and influences
 Site visual inspection and gathering of preliminary data
 Preliminary estimations and evaluation with existing data, by row mathematical and numerical tools, physical modeling or empirical
formulations.
 Review of projects of references.
 Preliminary hypothesis of natural and physical functioning of coastal processes
 Determination of needed detailed data and location of surveys (local winds, waves, flow velocities, sea levels, sediments, topography,
batimetry, geological and geotechnical information) for models selection, validation and callibrations*.
 Project budget estimation, presentation and approval by client
 Surveying, measurements, data filtering and process
 Model calibration
 Testing hypothesis, chek-out of results and validation.
 Coastal System Diagnostic. Sensitiveness analysis –what if?-
 Alternatives of solutions, impacts, risk and consecuences.
 Dimensions and Concept Design of Solution.
 Cost benefits analysis. Selection of best alternatives. Detailed measurements and adjustments.
 Final evaluation. Discussion of results, final solution (Description, construction specifications, BOQ, Drawings, Program)
 Delivery of final solution.
 Monitoring and Control of Coastal Project System
 Lessons learnt
* To counter the recurring problem of lack of data (waves, currents, other), a major tenet of coastal engineering should be to design ﬂexibility wherever possible
into every project to correct for unknown parameters and poorly estimated factors and to allow for ﬁne-tuning of the project afterwards.

Engineering approach to coastal engineering
The best understanding of coastal processes, including the nearshore ﬂows
and the resulting sediment transport, and the ability to transform it into
effective engineering measures require the following:
 A blend of analytical capability,
 An interest in the workings of nature,
 The ability to interpret many complex and apparently conﬂicting
pieces of evidence, and
 4. Experience gained from studying a variety of shorelines and working with
many coastal projects.

Engineering approach to coastal engineering
 End of presentation.Thank for attention!

Coastal engineering introduction

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Coastal engineering introduction